They did it in 2008 or 2009? I forget, seemed like it worked out really well then. didn't just lay the wood out, they build a frame and laid it out, so it was in place and sturdy. I would love to see them do it again.

Sorry, but I've attended every HB event since the league split.
The turf has always been laid directly on the sand.
Do you have any idea of how many 4x8 sheets of plywood needed to cover the ground of one 7-man field? That's approximately 560 sheets of plywood, which is hardly practical even if one's opinion believes there is an advantage to using it. I can imagine diving into a lifted corner of plywood would be just as dangerous as falling on an exposed spike or stake.
They've used plywood in the past for pathways, making transporting gear bags and equipment easier.

if the nppl used cheap plywood and osb and also built a very simple platform underneath my math says it would cost and additional 12,000 per field. That seems a little unreasonable.
It sucks sliding on the turf laid over the sand but its awesome to play on the beach and every other team has to deal with it. Just deal with it.

been to hb multiple times never had any problems with playing on the turf on the sand, plywood would be stupid like terry said, its not gonna be level leaving a bunch of raised edges, ouch that would hurt.